Method of producing zirconium tetrafluoride



l atented July 8, 1952 7 43 Memos jot: momma ZIRCONIUM TETRAFLUORIDEHarley A. Wilhelm and Kenneth A.=Wal'sh, Ames,

Iowa, assignors to the United Statesof America as represented by theUnitedStates Atomic I a Energy Commission 1 This invention deals withthe production of zirconium tetrafiuoride from a zirconium chloride andhydrogen fluoride.

It is an object of this invention to provide a process by which azirconium tetrafluoride is" produced which does not easily hydrolyze inmoist air. 1

It is another object of this invention to provide a process by which azirconium tetrafluoride is produced which is characterized by itsnonhygroscopic character and which thus is free from a tendency to cake.

It is still another object of this invention to provide a process forthe production of zirconium tetra-fluoride of a relatively high degreeof density.

These and other objects are accomplished by contacting a zirconiumchloride with gaseous hydrogen fluoride at a temperatureof about 50 C.until at least 90% of the chloride has been converted to the fluorideand thereafter continuing fluorination to completion of the reaction ata temperature of approximately 300 C.

It has been found that by carrying out the fiuorination in two stages,as has just been set forth, a product of considerably superior qualitiesis obtained. The treatment at 300 C. is responsible for thenonhydrolyzing and nonhygroscopic properties of the final product. Iffluorination is carried out exclusively at a higher temperature, morespecifically substantially above 50 C., the product cakes andfluorination cannot readily be brought to completion in the innerregions of the cake. If the fiuorination is carried out below 50 C.,condensation of the hydrogen fluoride takes place in the reactor whichagain makes the process poorly eificient. It thus will be obvious thatcombination of the temperatures forming the crux of the process of theinvention is critical. The second step, in addition to causing a productwhich is stable in moist air, also reconverts any zirconium oxide whichmight have formed by hydrolysis of the low temperature zirconiumtetrafluoride. V

The reaction which proceeds according to the equation ZrCl4+4=HF-ZrF4+4I-ICI is exothermic and proceeds at low temperature. An analysisof the reaction gases leaving the reaction vessel, and in particulartheir content of hydrochloric acid, is indicative of the stage andprogress of the reaction.

chlorides found especially well suitable for the process of thisinvention are zirconium tetrachloride and a complex formed of phosphorusoxychloride and zirconium tetrachloride.

NoDra wing. Application March.%, 1951', l

jjSeriailNo.218 ,080 v1 a Ulaims; (01.231 s's was inveterate phorusprobably was volatilized as POFa.

rosive action of the reagents may be used for the process of thisinvention, particularly gOOd results have been obtainedby the use ofgraphite trays which were enclosed in a copper jacket for the first stepand a similarly constructed Monel metal unit for the second step.

In the following, two examples are given for the purpose of illustratingthe process of this in- I vention but not with the intention to limitthe invention to the details given therein.

Example I One and one-half inch deep layers of zirconium tetrachloridewere filled into cylindrical graphite trays which were stacked on top ofeach other. In one'batch 1500 g. of zirconium tetrachloride was treated.The material was first brought to a temperature of C., and hydrogenfluoride was then introduced into the furnace. The hydrogen fluoride wasat a pressure slightly above Example II A complex of zirconiumtetrachloride with phosphorus oxychloride was heated in order to remove,by distillation, all of the hafnium contaminating the zirconiumchloride. The residue, which melts during this distillation step, wascooled. This solidified residue was then heated to 50 C., and hydrogenfluoride was passed over the heated material at slightlysuperatmospheric pressure for six and one-half hours. .A yield of about93% zirconium tetrafluoride wa obtained. The product obtained was awhite, porous solid free from chlorine and phosphorus. The phos- Thissolid product was then ground whereby a fluffy material was obtained. Ithydrolyzed easily when in contact with moist air. The material was thenconverted to a nonhydrolyzable .substance by heating it for two hours at300 C. in a hydrogen fluoride atmosphere.

I It i obvious from the two examples that the consistency of thezirconium chloride originally which withstandsthecor- 3 used is notaltered by the reaction. If, however, a product of higher density isdesirable, the product obtained by the process of this invention may besubjected to a sublimation step at 800 C. in a vacuum, or atsubstantially reduced pressure,

whereby: the. density of the fluoride. is. increased, It will beunderstood that this invention is not to be limited to the details givenherein but that it may be modified within the scope of the ap;

1. A process for the pr ducti n-of zirconium.

pended claims.

What is claimed is:

tetrafiuoride, which comprises reacting: a nirconium chloride withgaseous hydrogenfluoride'at a temperature of about 50 C. until at least90% of the zirconium compound has been converted to zirconiumtetrafiuoride, and then reacting the product to completion with hydrogenfiuoride at a temperature of about 300 C. whereby a mac-- ticallynonhydrolyzable zirconium tetrafluoride isproduced.

nium tetrafiuoride obtained is heated to about 800 C. under reducedpressure whereby the fluoride sublimes and a fluoride of increaseddensity results. i V

r HARLEY A. WILHEIM.

KENNETH A. WALSH.

REFERENCES CITED The following references are of record in the file ofthis. patent:

Welter, Chemiker Zeitung, volume 32, pages 606607 (1908).

1. A PROCESS FOR THE PRODUCTION OF ZIRCONIUM TETRAFLUORIDE, WHICHCOMPRISES REACTING A ZIRCONIUM CHLORIDE WITH GASEOUS HYDROGEN FLUORIDEAT A TEMPERATRE OF ABOUT 50* C. UNTIL AT LEAST 90% OF THE ZIRCONIUMCOMPOUND HAS BEEN CONVERTED TO ZIRCONIUM TETRAFLUORIDE, AND THENREACTING THE PRODUCT TO COMPLETION WITH HYDROGEN FLUORIDE AT ATEMPERATURE OF ABOUT 300* C. WHEREBY A PRACTICALLY NONHYDROLYZABLEZIRCONIUM TETRAFLUORIDE IS PRODUCED.